Vulcanization of rubber with aromatic sulfonamide activators



Patented Mar. 25, 1952 VULCANIZATIdN OF RUBBER WITH ARO- MA'IIC SULFONAMIDE ACTIVATOBS Andrew Tomlin, Hudson, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application July '12, 1949,

Serial No. 104,395

16 Claims. 260'79.5)

This invention relates to the vulcanization of rubber. More particularly it relates to the vulcanization of rubber with a new class of activators of vulcanization acceleration and to the vulcanized products resulting thereby.

2 attained by vulcanizing a vulcanizable rubber stock in which has been incorporated in addition to a primary organic vulcanization accelerator an aromatic sulfonamide of the general formula In the compounding of rubber, both natural I I and synthetic, improvements have ben constantly H 1 sought, particularly in respect to the more ef- 0 ficient and more economical use of vulcanization where R is an aromatic radical such as a phenyl,

accelerators. While many accelera rs, p tolyl, Xy1y1,xenyl, or na hthyl radical and where produce vulcanizates having acceptable physical R1 i a hydrogen t or an alkyl group ch s pr p rti s, t has l n b wn t by the a methyl, ethyl, propyl, isopropyl, or butyl radical, incorporation into thecompounded stock of acor a, higher alkyl group suchas heptyl or ethyl tivators of acceleration such as dibutyl am- 1 monium oleate in addition to a prim ry organic The new activators of themselves possess little vulcaniza i n acc 1 ra 0r, greater ease in pr if any accelerating activity, however, when emcessing and a better vulcanizate is obtained. pl yed in conjunction with such primary organic t iS a ject o this ve t o to provide a vulcanization accelerators as the aromatic and class of activators which are capa e of assisting non-aromatic substituted thiazole sulfides, and p y Organic v l aniza io aficelelatol's 1 0 thiazole sulfenamides, and other thiazole type SeSSing inherent Weaknesses, c as ineflicient accelerators, the dithiocarbamates, and the Vulcanizing c t d b y, and D thiuram monoand disulfides the accelerating persibility in rubber stocks, thus causing uneven ti i unexpectedly increased beyond that cures which in turn result in -u f D D- which would be expected from the mere combined erties and erratic performance in service. It is use of th two s bstances. i also an object of this invention to decrease the Alth h n the aromatic sulfonamides of the time Of vu ca i at o A further Object is to above described general formula produce activapr vi e a wi r choice of urin conditio such tion, the best results are obtained with those that a series of combinations varying in scorch sulfonamides wherein R1 is a hydrogen atom or and Cu p p rties may be obtained. For an alkyl group containing less than four carbon example, the ratio of activator to accelerator may toms. As specific examples of this group are the v p nding upon the type of rubber, type f toluene (or tolyl) sulfonamides, benzene (or stock, t mp atur o u time of cure. the phenyl) sulfonamide, N-methyl oand p-toluene ticular vulcanization accelerator, and the obsulfonamide, N-isopropyl benzene sulfonamide, jectives of the compounder, that is whether a low N-isopropyl oand p-toluene sulfonamide, and or high modulus is desired or a short or long various mixtures, particularly the eutectic mixcure is required. Other objects will appear tures, thereof. j

hereinafter. As exemplary of the activating properties of It has been found in accordance with this inthe aromatic sulfonamides, the following stocks vention that the above mentioned objects are were compounded comprising Parts by weight- Stocks The above stocks so compounded were vulcanized in the usual manner by heating in a press for diiferent periods of time. The physical properties of the respective cured stocks are set forth below:

The above stocks so compounded were vulcanized in the usual manner by heating in a press for difierent periods of time at 142 C.

Table I Modulus in lbs./ in.

at elongations of- Tensile at Ultimate Stock Minutes Cure Break lbs./ Elongation 1n. Per cent 300% 500% 700% l0@142C 80 245 840 1,155 760 @l42C.

15@142O 80 220 790 1, 230 800 15@142C 130 393 l, 233 2, 103 800 142C- 70 235 830 1, 715 840 20@142C 110 400 1, 215 1, 960 810 20@142C 120 375 1, 220 2, 010 810 15@142 O 120 325 1, 195 2, 195 830 l5@1420. 180 590 2, 070 2, 910 763 15@l42 O 230 890 013 3, 463 743 15@138O 165 490 1, 220 1, 620 780 15@l38C 376 1, 130 3, 350 3, 350 700 15@138 384 l, 060 24 690 1 NO cure.

As further exemplary of the activating properties of aromatic sulfonamides, the following synthetic rubber stocks were compounded comprising The physical properties of the respective cured stocks are set forth below:

Table III Modulus in lbs/in. 1 Parts by weight Minutes at elongations oi Tensile at Ultimate Stock cure at Break in Elongation Stocks 142 C lbs/in. 1 percent K L M 300% 500% 700% GR-S rubber 100 100 100 15 Carbon black--. 40 40 15 110 250 855 1, 210 780 Zinc oxide. 3 3 15 140 330 1,070 1, 685 795 Sulfur 2 2 15 110 305 910 l, 010 730 Mercaptobenzothiazole 1 1 30 Eutectic mixture containing: 30 140 417 1, 340 2, 197 793 40% ortho toluene sulionamide o 5 1 0 30 143 463 l, 550 2, 373 793 60% para toluene sulfonamide 30 170 517 1, 040 2, 213 770 137 427 1, 573 2, 287 783 2 it? 23% Hit 4 2,507 787 The above synthetic rubber stocks so com 45 m0 470 1, 630 2, 605 805 pounded were vulcanized in the usual manner by'heating in a press for different periods of time at 142 C. The physical properties ofthe respective cured stocks are set forth below:

As exemplary of the activating properties of N-alkyl substituted aromatic sulfonamides the Parts by weight N O P Q sentences-.-

Benzothiazyl disulfide N-ethyl-p-toluene sulionami N -ethylbenzene sulfonamide -N-isopropyl-benzeue sulfonamide following gum stockswere compounded compris- 1 N o cure.

It is obvious from the above data the aromatic sulfonamides are a class of compounds which exert a marked activating effect on the cure rate. The new activators disperse readily and rapidly in rubber stocks, both natural and synthetic.

Smaller amounts of the aromatic sulfonamide activators may be employed than those indicated in the examples. Amounts as small as 0.2% on the-rubber of aromatic sulfonamide exhibit activating properties. Amounts higher than those specifically shown, as for example 2%, may be employed depending upon the conditions of compounding and the objectives of the compounder.

By the term a rubber as employed in the specification and appended claims, unless otherwise modified, is meant natural as well as synthetic rubbers which are capable of vulcanization when heated with sulfur and includes latices and reclaims of such materials whether or not admixed with pigments, fillers, softeners, antioxidants, etc.

While specific embodiments of the invention have been described herein, it will be understood that the invention is not so limited but that various modifications may be made therein without departing from the spirit of the inven-- tion or scope of the appended claims.

What is claimed is:

1'. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of an aromatic sulfonamide of the formula where R is selected from the group consisting of unsubstituted and methyl substituted aromatic hydrocarbon radicals containing not more than 12 carbon atoms and where R1 is selected from the group consisting of hydrogen atoms and alkyl radicals containing not more than 8 carbon atoms.

2. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of an aromatic sulfonamide of the formula where R is selected from the group consisting of unsubstituted and methyl substituted aromatic hydrocarbon radicals containing not more than 12 carbon atoms and where R1 is an alkyl group containing less than four carbon atoms.

3. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of an aromatic sulfonamide of the formula where R is selected from the group consisting of unsubstituted and methyl substituted aromatic hydrocarbon radicals containing not more than 12 carbon atoms.

4. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of a toluene hydrocarbon sulfonamide of the structure C7H7SO2NH2.

5. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of para toluene sulfonamide.

6. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of ortho toluene sulfonamide.

7. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of an N-ethyl toluene sulfonamide.

8. The method of vulcanizing a rubber which comprises heating a rubber, sulfur, and a primary organic sulfur containing vulcanization accelerator in the presence of N-ethyl para toluene sulfonamide.

9.. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of an aromatic sulfonamide of the formula where R is selected from the group consisting of unsubstituted and methyl substituted aromatic hydrocarbon radicals containing not more than 12 carbon atoms and where R1 is selected from the group consisting of hydrogen atoms and. alkyl radicals containing not more than 8 carbon atoms.

10. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of an aromatic sulfonamide of the formula where R is selected from the group consisting of unsubstituted and methyl substituted aromatic hydrocarbon radicals containing not more than 12 carbon atoms and where R1 is an alkyl group containing less than four carbon atoms.

11. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of an aromatic sulfonamide of the formula where R is selected from the group consisting of unsubstituted and methyl substituted aromatic hydrocarbon radicals containing not more than 12 carbon atoms.

12. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of a toluene hydrocarbon sulfonamide of the structure C'1H7SO2NH2.

13. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of para toluene sulfonamide.

14. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of ortho toluene sul-' fonamide.

15. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of an N-ethyl toluene sulfonamide.

16. The vulcanized rubber product obtained by heating a rubber, sulfur, and an organic sulfur containing vulcanization accelerator in the presence of a small amount of N-ethyl para toluene sulfonamide.

NDREW TOML-IN.

REFERENCE S CITED UNITED STATES PATENTS Y Name Date Orthner et a1. Aug. 29, 1933 Number 

1. THE METHOD OF VULCANIZING A RUBBER WHICH COMPRISES HEATING A RUBBER, SULFUR, AND A PRIMARY ORGANIC SULFUR CONTAINING VULCANIZATION ACCELERATOR IN THE PRESENCE OF AN AROMATIC SULFONAMIDE OF THE FORMULA 